A typical engine has an exhaust manifold that receives and combines exhaust gasses from each cylinder of the engine and directs the combined exhaust gasses from the engine to an exhaust system and eventually to the atmosphere. An operating variable is typically monitored with a feedback sensor located in the exhaust stream which provides a feedback signal to an electronic controller. As an example, the controller may provide data relative to the air/fuel ratio of the internal combustion engine.
One common variable that is monitored by the feedback sensor is oxygen concentration in exhaust gases. When the monitored variable is exhaust oxygen concentration in exhaust gases, the feedback sensor may be a narrow-band oxygen sensor.
The exhaust sensor in some internal combustion engine directly measures oxygen content of the combined exhaust from all cylinders in the engine. This data typically does not directly correlate to the actual ratio between air and fuel in each individual cylinder that is part of the internal combustion engine.